Fel posted that now he has finished conviction, he gonna have a break, then possibly work on this series.
Last time, they knocked out a Chinese fleet and realised they must have a lost sky dragon library. Which includes at minimum the potion needed to give humans magical earth protection. Apparently, it could shared amongst dragons.
There is a chance earth dragons can achieve a minimum of flight if they blood linked to enough human magic users.

The human magicians now have their talismans, so I am expecting so magical action there.

We know there is apparently more than one formula in those books, the known one grants elemental immunity. Imagine if the unknown one could grant elemental ability. Not all fire, water or air dragons are magicians but they do all posses the ability to manipulate their element. I wonder why the earth dragons don't have a similar ability. It might simply have been lost or forgotten over the years. We know there are earth spells, they are simply the hardest and most advanced magics around. Using such a formulas, could an earth ability be created? The chromatic dragons while all magicians, they each have their own talent. It could be possible that a similar process could be created.
I doubt the earth dragons would ever be true magicians, but I can see them developing magical strength and power.